Install test app2 per test class for HostsideConnOnActivityStartTest

With installing test apps per test class instead of test cases,
the total execution time tests are improved from 1m56s to 1m34s
in local trials.

Notes: 1. This is a demonstration CL to other Hostside*Tests to show
          how to make app2 can be installed per test class.
       2. The method that executed per test class should not shadow
          the method in the base class, see the doc of @BeforeClass.

Test: atest HostsideConnOnActivityStartTest
Bug: 289002798
Change-Id: Ia9875f0a9fdcb4fb4c55736034b56aad0491d451